CN115427169A

CN115427169A - Method for producing a cured three-dimensional shaped body layer by layer, shaped body obtainable by said method and use thereof

Info

Publication number: CN115427169A
Application number: CN202180027483.2A
Authority: CN
Inventors: D·***斯; D·波尔萨基维奇
Original assignee: ASK Chemicals GmbH
Current assignee: ASK Chemicals GmbH
Priority date: 2020-06-15
Filing date: 2021-06-14
Publication date: 2022-12-02
Also published as: WO2021254953A1; MX2022012744A; EP4164822A1; US20230191653A1; CA3170459A1; JP2023528584A; BR112022017502A2; DE102020003562A1

Abstract

The invention relates to a method for producing a cured three-dimensional molded body layer by layer, wherein the method at least comprises the following steps: (i) providing an adhesive comprising at least the following components: a) Monomeric furfuryl alcohol and optionally a resin component comprising at least a furan resin, wherein about 60-100 wt% of monomeric furfuryl alcohol, based on the total of monomeric furfuryl alcohol and resin component, is present in the binder, and b) a hardener component selected from methanesulfonic acid, benzenesulfonic acid, and mixtures thereof, (ii) providing a layer of fire resistant molding material to provide a layer of molding material, (iii) optionally applying components a) or b) of the binder onto at least a portion of the layer of molding material separately from the fire resistant molding material, (iv) applying other components of the binder separately from the components described in step (iii), wherein step (iv) may be performed before or after step (iii), or step (iv) may be combined with step (ii), and (v) optionally repeating steps (ii), (iii), and (iv) one or several times. The shaped bodies thus obtained and their use are also disclosed.

Description

Method for producing a cured three-dimensional shaped body layer by layer, shaped body obtainable by said method and use thereof

The invention relates to a method for preparing a solidified three-dimensional forming body layer by layer. The shaped bodies produced in this way are particularly suitable for use as casting cores and molds for metal casting.

Various methods are known for producing three-dimensional shaped bodies layer by layer. By these methods, even objects with the most complex geometries can be directly prepared layer by layer from CAD data by 3D printing without the need for molds. This is not possible in conventional methods requiring a mold.

WO 2001/068336 discloses various adhesives for layer-by-layer preparation. In particular, the use of furan resins (not described in further detail) with at least 50% furfuryl alcohol and about 4% ethylene glycol as binder component is also cited. The resin component of the binder is sprayed layer by layer over the entire working surface of the bulk molding material and then also cured layer by layer, but optionally with the application of a hardener such as an organic acid. As the organic acid, toluenesulfonic acid is disclosed.

WO 01/72502 describes a variant of this method in which a liquid binder material, in particular a furan resin (not described in further detail) and a liquid hardener (such as toluene sulfonic acid) are selectively applied to the part to be cured in succession in the order of resin component and then hardener.

According to WO 03/103932, the resin component of the binder is no longer applied layer by means of the print head, but is mixed directly with the molding material and applied layer by layer with the molding material. The mixture of resin component and molding material is then cured by selective application of sulfurous acid as a hardener.

WO 2018/224093 discloses another method for layer-by-layer production of cured three-dimensional shaped bodies. In this document, a resin component is used which comprises a furan resin which is the reaction product of at least one aldehyde compound and furfuryl alcohol, and optionally a nitrogen-containing compound and/or a phenol compound, wherein the nitrogen content of the resin component is less than 5% by weight, and wherein the resin component comprises more than 5% by weight and less than 50% by weight of monomeric furfuryl alcohol, based on the resin component.

In WO 2004/110719 the order of addition is reversed. First, the molding material is premixed with the hardener, and then the resin component is selectively applied layer by layer. As hardeners, acids, amines and esters are described. The hardener is not described in further detail.

DE 10 2014 106 describes a method for the layer-by-layer production of objects, in which a molding material is hardened in layers by means of cresol resins and esters.

In particular, the acid/furan resin system of WO 2004/110719 and the ester/cresol resin system of DE 10 2014 106 have been accepted in practice to some extent for the layer-by-layer preparation of shaped bodies, and for the development of new castings and the production of single parts or small series when conventional production using molds is too complex and expensive, or only feasible in complex core packages.

The disadvantage of the acid/furan resin system is that the moldings produced according to this process must first be freed from adhering and non-printing mixtures of molding material and acid or resin components in a complicated process. The person performing this task is exposed to solvents and binder vapors in addition to dust.

Object of the Invention

It is therefore an object of the present invention to provide a process for the layer-by-layer production of cured three-dimensional shaped bodies, in which the tendency of the unbonded mixture to adhere to the resulting shaped body is minimized. Thus, the effort required to remove the unbonded sand from the bonded area is minimized. In addition to saving time, exposure of workers to solvent and/or adhesive vapors is minimized. It is another object of the present invention to provide a method for producing a three-dimensional shaped body having high flexural strength.

The fact that the so-called job boxes of 3D printers can be used with greater space efficiency is a further advantage, i.e. the moulded bodies can be positioned closer to each other without the risk of objects sticking to each other. Furthermore, since the areas which have already reacted and cured slightly are significantly reduced, the unprinted molding material mixture can be more easily reintroduced into the process.

Summary of The Invention

It has surprisingly been found that these objects can be achieved by a process for the layer-by-layer production of a cured three-dimensional shaped body, wherein the process comprises at least:

(i) Providing an adhesive comprising at least the following components:

a) A monomeric furfuryl alcohol and optionally a resin component comprising at least a furan resin, wherein about 60-100% by weight of the monomeric furfuryl alcohol, based on the total of the monomeric furfuryl alcohol and the resin component, is present in the binder, and

b) A hardener component selected from the group consisting of methanesulfonic acid, benzenesulfonic acid, and mixtures thereof,

(ii) Providing a layer of a fire resistant moulding material to provide a layer of moulding material,

(iii) Optionally applying components a) or b) of the binder to the molding material separately from the flame-resistant molding material

On at least a part of the material layer,

(iv) (iv) applying the other components of the adhesive separately from the components described in step (iii), wherein step (iv) may be performed before or after step (iii), or step (iv) may be combined with step (ii), and

(v) (iv) optionally repeating steps (ii), (iii) and (iv) once or several times. A particularly advantageous embodiment of the process according to the invention comprises at least the following steps:

alpha) preparing a mixture of a flame-resistant molding material and a hardener component b),

beta) providing a layer of a mixture of a flame-resistant molding material and a hardener component b),

γ) selectively applying component a) onto at least a portion of the layer, and

δ) optionally repeating steps β) and γ) one or several times.

The invention further relates to a shaped body which can be obtained by the method according to the invention. The shaped bodies can be used for metal casting, in particular for iron, steel, copper or aluminum casting.

Drawings

Figure 1 shows the specimen geometry used to quantify the sticking that occurred during the preparation process.

Detailed Description

The method of the invention comprises at least:

(i) Providing an adhesive comprising at least the following components:

(iii) Optionally applying component a) or b) of the binder separately from the flame-resistant molding material to at least a part of the layer of molding material,

(v) (iv) optionally repeating steps (ii), (iii) and (iv) once or several times.

A particularly advantageous embodiment of the process of the invention comprises at least the following steps:

γ) selectively applying component a) onto at least a portion of the layer, and

δ) optionally repeating steps β) and γ) one or several times.

Flame-resistant moulding materials

The flame-resistant molding material is not particularly limited. Any particulate solid may be used as the fire resistant molding material. Preferably, the refractory molding material is in a free-flowing state. Conventional and known materials for the preparation of casting molds can be used in pure form or as mixtures thereof as refractory molding materials. Suitable materials are, for example, quartz sand, zircon sand or chromium ore sand, olivine, vermiculite, bauxite, fireclay and fire-resistant moulding materials which have been prepared artificially and/or are obtainable from synthetic materials, for example hollow microspheres. Quartz sand is particularly preferred for cost reasons. Flame-resistant molding materials are materials having a high melting point (melting temperature). Preferably, the refractory molding materials have a melting point of at least about 600 ℃, more preferably at least about 900 ℃, especially preferably at least about 1200 ℃, and especially preferably at least about 1500 ℃.

The average particle size of the flame-resistant molding materials is generally from about 30 to about 500. Mu.m, preferably from about 40 to 400 μm, particularly preferably from about 50 to 250. Mu.m. The particle size can be determined, for example, by sieving according to DIN ISO 3310.

Moulding material additive

In addition to the flame-resistant molding material, the molding material layer may also contain additional solids. Within the framework of the present invention, they are referred to as molding material additives. They are usually particulate solids. The molding material additives generally have an average particle diameter of from about 30 to about 500. Mu.m, preferably from about 40 to about 400. Mu.m, particularly preferably from about 50 to about 250. Mu.m. The particle size can be determined, for example, by sieving according to DIN ISO 3310.

The flame-resistant molding materials and, if present, the molding material additives are referred to as molding material mixtures. Examples of molding material additives include organic or inorganic additives such as iron oxides, silicates, aluminates, hollow microspheres, sawdust or starch and mixtures thereof. They can be added to refractory molding materials to avoid casting defects.

The amount of the molding material additives is not particularly restricted, and is generally up to about 10% by weight, preferably up to about 7% by weight, particularly preferably up to about 1% by weight, based on the molding material mixture.

The amount of the flame-resistant molding material in the molding material mixture is not particularly limited. The flame-resistant molding material preferably constitutes at least about 80% by weight, more preferably at least about 90% by weight, particularly preferably at least about 93% by weight and particularly preferably 99% by weight of the molding material mixture.

In a preferred embodiment, amorphous SiO ₂ As an additive to molding materials.

Adhesive agent

The adhesive is a multi-component system comprising at least:

b) A hardener component selected from the group consisting of methanesulfonic acid, benzenesulfonic acid, and mixtures thereof.

Within the framework of the present invention, all liquid components used in the process of the invention are considered as components of the adhesive.

Resin component

Within the framework of the present invention, all polymer and oligomer components of the adhesive are referred to as resin components.

The adhesive may optionally comprise a resin component. The resin component, if present, comprises a furan resin. The furan resin is not particularly limited and may be any furan resin known in the art.

Furan resins are generally obtained from furan compounds, in particular from furfuryl alcohol and aldehyde compounds, in particular formaldehyde. In addition to furfuryl alcohol, furfuryl alcohol derivatives such as 2,5-bis (hydroxymethyl) furan, the methyl or ethyl ether of 2,5-bis (hydroxymethyl) furan, or 5-hydroxymethylfurfural may be used as comonomers.

Generally, compounds of the formula R-CHO are used as aldehyde compounds, where R is a hydrogen atom or a hydrocarbon radical having preferably from 1 to 8, particularly preferably from 1 to 3, carbon atoms. Examples include formaldehyde, acetaldehyde, propionaldehyde, and butyraldehyde. Furfural (furfuryl aldehyde) and glyoxal may also be used. Mixtures of more than one aldehyde compound are also possible. Particular preference is given to formaldehyde or mixtures which contain formaldehyde predominantly, based on the molar amount of aldehyde. Formaldehyde is most preferred.

The molar ratio of furan compounds (especially furfuryl alcohol) to aldehydes (especially formaldehyde) is generally greater than or equal to about 0.5, preferably from about 1.2 to about 1.5, more preferably from about 1:2 to about 0.8, and especially preferably from about 1.

Further, when the aldehyde compound and the furan compound are reacted, one or more other compounds may be reacted, such as nitrogen-containing compounds, e.g., urea, furfuryl alcohol derivatives, and/or phenol compounds.

Optionally, the resin component may include a nitrogen-containing compound to improve the properties, such as strength, of the resulting part. They are not particularly limited. Suitable nitrogen-containing compounds are, for example, urea derivatives, such as urea itself, melamine or ethylene urea, or amines, such as ammonia and triethylamine, amino alcohols, such as monoethanolamine or 2-amino-2-methyl-1-propanol. In a particularly preferred embodiment, urea, triethylamine or monoethanolamine, in particular urea, is used.

The nitrogen-containing compound can be reacted directly with the other reactants or their precondensates or, in a preferred variant, as a separate precondensate, in particular in the form of a urea derivative, for example preferably urea itself, which is condensed with an aldehyde, preferably formaldehyde, and optionally with furfuryl alcohol or furfuryl alcohol derivatives.

The amount of nitrogen-containing compound may be selected such that the total nitrogen content (N) of the resin component, as determined according to Kjeldahl (according to DIN 169916-02-B2 or VDG specification P70), is at most about 5% by weight, preferably at most about 3.5% by weight, particularly preferably at most about 2% by weight, so that surface defects due to the presence of nitrogen are reduced or avoided in the resulting casting.

Optionally, a phenolic compound may be present in the resin component to improve industrial sand properties, such as strength. The phenol compound is not particularly limited. However, suitable phenolic compounds are characterized by one or more aromatic rings and at least one hydroxyl substitution on these rings. Examples include, in addition to phenol itself, substituted phenols such as cresol or nonylphenol, 1,2-dihydroxybenzene (catechol), 1,3-dihydroxyphenyl (resorcinol), cashew nut shell oil, i.e. a mixture of cardanol and cardol, or 1,4-dihydroxybenzene (hydroquinone) or phenolic compounds such as bisphenol a or mixtures thereof. Phenol is particularly preferred as the phenol compound.

The phenolic compound may be reacted directly with the other reactant or a precondensate thereof. Furthermore, the reaction product of phenol and formaldehyde in the form of a phenolic resin prepared under alkaline conditions may be added to the resin component.

The total content of free phenol is preferably up to about 1% by weight, based on the binder (determined by gas chromatography).

The total amount of furan compounds (especially furfuryl alcohol) and aldehyde compounds (especially formaldehyde), both as monomers, is at least about 60 wt.%, preferably at least about 70 wt.%, particularly preferably at least about 80 wt.%, based on all reactants used.

The reaction may be carried out in the presence of an acid catalyst, preferably pK at 25 ℃ _a A value of 2.5 or more, more preferably pK _a Values of about 2.7 to about 6.0, with those having pKa values of about 3.0 to about 5.0 being especially preferred.

In the preparation of furan resins, the weak acids, mixtures thereof and salts thereof, are preferably pK at 25 ℃ _a A value of 2.5 or more, more preferably pK _a Values of about 2.7 to about 6.0, with pK being particularly preferred _a Those having values of from about 3.0 to about 5.0 are useful as acid catalysts. They preferably comprise organic acids, such as benzoic acid, lactic acid, adipic acid, citric acid or salicylic acid. As an example of the salt, zinc acetate is mentioned.

Suitable furan resins are described, for example, in WO 2004/7110719, WO 2018/224093, DE 20 2011 110 617U1 and DE 10 2014 002 679A1, which are incorporated herein by reference.

The furan resin may be present in the resin component in an amount of from 50 to about 100 wt%, preferably from 60 to about 99 wt%, particularly preferably from 30 to 97 wt%.

In a preferred embodiment, the resin component may further comprise a urea formaldehyde resin.

The urea-formaldehyde resin may be present in the resin component in an amount of from 0 to about 25 weight percent, preferably from about 1 to about 20 weight percent, and particularly preferably from about 3 to about 15 weight percent. The urea resin is not particularly limited. Urea-formaldehyde resins are obtainable by reacting aldehyde compounds, in particular formaldehyde, with nitrogen-containing monomers, in particular urea.

The molar ratio of urea to formaldehyde may be up to about 1, preferably from about 1:1 to about 1:5, more preferably from about 1:1 to 1:4, and especially preferably from about 1.2 to about 1:3. Strong acids, mixtures thereof and salts thereof, preferably pK at 25 ℃ _a A value greater than or equal to about-2.5, more preferably a pK _a Values of about-2.5 to about 2.0, with pK being particularly preferred _a Those having values of from about 0 to about 2.0 are useful as acid catalysts for the reaction of urea and formaldehyde. They preferably comprise p-toluenesulfonic acid or phosphates, such as sodium phosphate.

Urea-formaldehyde resins have a positive influence on the strength development of the shaped bodies produced by the layer-by-layer production process.

In addition, the resin component may comprise a phenolic resin, in particular a cresol resin. The phenolic resin may be present in the resin component in an amount of from 0 to about 25 wt%, preferably from 0 to about 20 wt%, particularly preferably from 0 to about 15 wt%.

Monomeric furfuryl alcohol

The binder comprises about 60-100 wt% of monomeric furfuryl alcohol, based on the sum of the resin component and the monomeric furfuryl alcohol, i.e., if the sum of the resin component, the monomeric furfuryl alcohol, and the optional component is taken as 100 parts by weight, the amount of monomeric furfuryl alcohol is about 60-100 parts by weight. Preferably, the amount of monomeric furfuryl alcohol is from about 60 to about 99 weight percent, more preferably from about 60 to about 98 weight percent, and even more preferably from about 70 to about 98 weight percent, based on the sum of the resin component, monomeric furfuryl alcohol, and optional components. The amount of monomeric furfuryl alcohol can be determined, for example, by gas chromatography (see VDG specification P70 "Bindemmettelpfung, brufung von flu segen

Furanharzen ", 3 rd edition, 4 months 1989).

It was found that a binder comprising from about 60 to 100 wt.% of monomeric furfuryl alcohol, based on the sum of the resin component and the monomeric furfuryl alcohol, results in shaped bodies that exhibit higher strength than shaped bodies prepared with binders having a lower furfuryl alcohol content. However, this increase in strength results in a significant increase in the amount of material that adheres to the part. It has surprisingly been found that not only the desired increased strength but also a reduction in the resulting adherends can be achieved by using the hardener component b) of the invention alone.

The monomeric furfuryl alcohol may be added as such to the binder. Alternatively or additionally, commercially available furan resins with corresponding residual monomeric furfuryl alcohol content may be used.

Hardener component

The hardener component b) consists of methanesulfonic acid, benzenesulfonic acid or mixtures thereof.

The amount of hardener component b) is preferably from about 0.05 to about 1.5% by weight, more preferably from about 0.01 to about 1.25% by weight, particularly preferably from about 0.05 to about 1% by weight, based on the amount of molding material mixture taken as 100% by weight.

Optional Components

The adhesive may contain additional optional components such as phenolic compounds, water, glycols, alcohols, solvents, plasticizers, cure modifiers, surface modifiers, or surfactants. Optional components can be used together with component a), together with component b), together with components a) and b), or separately from components a) and b).

Phenol compound

Optionally, phenolic compounds may be present to improve industrial sand properties, such as strength. The phenol compound is not particularly limited. However, suitable phenolic compounds are characterized by one or more aromatic rings and at least one hydroxyl substitution on these rings. Examples include, in addition to phenol itself, substituted phenols such as cresol or nonylphenol, 1,2-dihydroxybenzene (catechol), 1,3-dihydroxyphenyl (resorcinol), cashew nut shell oil, i.e. a mixture of cardanol and cardol, or 1,4-dihydroxybenzene (hydroquinone) or phenolic compounds such as bisphenol a or mixtures thereof. Resorcinol is particularly preferred as the phenolic compound. The phenolic compound is preferably applied together with component a).

Water (W)

The binder may optionally contain water for dilution.

The amount of water is not particularly limited; preferably, the amount of water is from about 0.009 to about 60 wt.%, more preferably from about 0.1 to about 50 wt.%, particularly preferably from about 0.5 to about 45 wt.%, particularly preferably from about 1 to about 40 wt.%, based on the binder.

Hardener component b) may optionally comprise water for dilution. The amount of water here is from 10 to 90% by weight, preferably from 25 to 75% by weight, more preferably from 40 to about 60% by weight, based on the hardener component b) taken as 100%.

The amount of water can be determined by Karl Fischer titration in accordance with DIN 51777.

Diols

Furthermore, the binder may comprise a glycol to improve the industrial sand properties of the resulting three-dimensional shaped body, in particular to improve its elasticity and reduce its brittleness. The diol is not particularly limited; any glycol may be used-polymeric glycols, such as polyethylene glycol, are also contemplated. Ethylene glycol, butyl diglycol and combinations thereof are preferred, with ethylene glycol being particularly preferred. The amount of the diol is not particularly limited; preferably, the diol is present in an amount of from about 0.5 to about 10 weight percent, more preferably from about 1 to about 5 weight percent, based on the amount of hardener component b) taken as 100 weight percent. Preferably, the diol is introduced together with component b).

Alcohol(s)

The adhesive may optionally further comprise C other than a diol _1-4 An alcohol (preferably ethanol) or a mixture thereof. The alcohol is used to optimize industrial sand performance. The amount of the alcohol is not particularly limited; preferably, the alcohol is present in an amount of about 1 to about 25 weight percent, more preferably about 2 to about 10 weight percent, based on the amount of binder.

Solvent(s)

In one embodiment, the adhesive may additionally comprise other solvents, in particular organic solvents comprising 1 to 25 carbon atoms, for example alcohols such as ethanol, propanol, 5-hydroxy-1,3-dioxane, 4-hydroxymethyl-1,3-dioxolane or tetrahydrofurfuryl alcohol, oxetanes such as trimethylolpropane oxetane, ketones such as acetone, or esters such as triacetin and propylene carbonate. The amount of the other solvent is not particularly limited; preferably, the additional solvent is present in an amount of about 1 to about 25 weight percent, more preferably about 2 to about 10 weight percent, based on the amount of binder.

Plasticizers and curing regulators

Conventional plasticizers or curing regulators may be included in the binder to adjust the strength and elasticity of the shaped bodies. These include, for example, diols or polyols having 2 to 12 carbon atoms, fatty acids, polysiloxanes or phthalates. Fatty acids such as oleic acid are particularly preferred.

The plasticizer or cure regulator is present in conventional amounts, which may range, for example, from 0 to about 25 weight percent, preferably from 0 to about 20 weight percent, more preferably from about 0.2 to about 15 weight percent, based on the resin component.

Surface modifier

Surface modifiers for adjusting surface tension and improving industrial sand performance may also be added to the binder. The use of silanes as surface modifiers is known from EP 1 137 500 A1. Suitable silanes include, for example, aminosilanes, epoxysilanes, mercaptosilanes, hydroxysilanes and ureidosilanes, such as gamma-hydroxypropyltrimethoxysilane, gamma-aminopropyltrimethoxysilane, 3-ureidopropyltriethoxysilane, gamma-mercaptopropyltrimethoxysilane, gamma-glycidoxypropyltrimethoxysilane, beta- (3,4-epoxy-cyclohexyl) -trimethoxysilane and N-beta- (aminoethyl) -gamma-aminopropyltrimethoxysilane or polysiloxanes.

The amount of surface modifier is within the conventional range and can be, for example, from 0 to about 5 weight percent, preferably from about 0.01 to about 2.00 weight percent, more preferably from about 0.05 to 1.00 weight percent, based on the resin component.

Surface active agent

To reduce the surface tension, surfactants such as cationic, anionic or nonionic surfactants can be used. Examples include carboxylates, sulfonates or sulfates as anionic surfactants, such as sodium 2-ethylhexyl sulfate, quaternary ammonium compounds as cationic surfactants, such as ester quaternaries, or alcohols, esters or ethoxylates as nonionic surfactants, such as polyalkylene glycol ethers. Modified siloxanes having both hydrophobic and hydrophilic portions are also contemplated, such as 3- (polyoxyethylene) propylheptamethyltrisiloxane. When selectively applied, they are preferably used with a resin component to facilitate application.

It was found to be particularly advantageous when the hardener component b) is used in the process of the invention in a mixture with water and optionally a diol, in particular ethylene glycol.

Hardener component b) is present in the mixture in an amount of from 10 to about 90% by weight, preferably from about 25 to about 75% by weight, more preferably from about 30 to about 70% by weight, and especially preferably from about 40 to about 60% by weight.

The diol is present in the mixture in an amount of from about 0 to about 15 weight percent, preferably from about 2 to about 10 weight percent, more preferably from about 4 to 8 weight percent.

Water is present in the mixture in an amount of about 10 to 90% by weight, preferably 25 to 75% by weight, more preferably 40 to 60% by weight, based on the hardener component b) taken as 100%.

Method for preparing solidified three-dimensional forming body layer by layer

The method for preparing the solidified three-dimensional forming body layer by layer at least comprises the following steps:

(i) Providing an adhesive:

(v) (iv) optionally repeating steps (ii), (iii) and (iv) once or several times.

Step (ii): providing a layer of a fire-resistant moulding material to provide a layer of moulding material

In the process of the invention, a layer of a flame-resistant molding material and optionally molding material additives is first applied. The thickness of this layer may, for example, be from about 0.03 to about 3mm, preferably from about 0.03 to about 1.5mm. In this step, if desired, one or more binder components can also be applied, for example by mixing them with the flame-resistant moulding material before the layer of flame-resistant moulding material is provided (combination of step (iv) and step (ii)).

Step (iii): optionally applying the components a) or b) of the binder separately from the flame-resistant molding material to at least one part of the molding material layer

Step (iv): (iv) applying the other components of the adhesive separately from the components described in step (iii)

The term "applying" means combining the two components together. This may be done non-selectively or selectively.

During non-selective application, one component may be applied to a surface (e.g., to a layer of molding material). Alternatively, one component can be mixed with another component (e.g., with the fire-resistant molding material) by a mixing device or manually.

During selective application, one component is applied to certain areas of the other component. During selective application, it is preferred to apply the component to only certain portions of another component. The selective application can be performed, for example, by a print head or similar application method. In one embodiment, the components to be applied may be applied through a mask. A mask is a sheet material having areas that are impermeable to the component to be applied and areas (e.g., apertures) through which the component to be applied can pass and contact certain areas of another component. Such as screen printing or stencil printing.

In a particularly preferred embodiment, the selective application is performed by a print head. This method is, for example, 3D printing, sometimes also referred to as "adhesive jetting". The components to be applied are applied by jet printing by means of a print head. 3D printing is an additive manufacturing method in which a powder material is adhered to a binder in predetermined areas to obtain a desired shaped body. The method is standardized, for example in VDI Guideline 3405.

In step (iii), component a) or component b) of the binder is applied to the portion of the layer of molding material to be cured. When components a) and b) of the adhesive are mixed and applied together, premature curing reactions may occur in the applicator (e.g., a print head). This can, for example, lead to clogging of the applicator (e.g., print head), resulting in reduced productivity. Thus, component a) is applied separately from hardener component b). The optional components can be added to component a) and/or hardener component b) or applied separately from these components. In order to reduce the number of steps, it is preferred to add optional components to component a) and/or hardener component b).

In a preferred embodiment, component a) is mixed with the flame-resistant molding material and the molding material additives, if any, and applied together with them as a molding material layer. The hardener component b) is then selectively applied to at least a part of the layer of molding material thus activated.

In a further particularly preferred embodiment, the hardener component b) is mixed with the flame-resistant molding material and the molding material additives, if any, and applied together with them as a molding material layer. Component a) is then selectively applied to at least a portion of the layer of molding material thus activated.

In a further preferred embodiment, the flame-resistant molding material and the molding material additives, if any, are mixed and provided as a molding material layer. Component a) and hardener component b) are then applied to the layer of moulding material by two separate print heads. In this connection, it has been found to be advantageous to apply one component to the surface (for example, the entire surface area of the layer of molding material) and to apply the other component selectively to the part of the layer of molding material to be cured.

The mixture of the flame-resistant molding material and the molding material additives, if any, and the hardener component b) or component a) can be applied, for example, at a temperature of from about 10 to about 45 ℃.

The selective application of components is known in the art and can be performed using conventional methods. The temperature (in 3D printing, the temperature of the print head) is not limited to room temperature, but may be about 20 to about 80 ℃, particularly 20 to about 40 ℃. Thus, components having a higher viscosity can also be applied easily.

When the adhesive component a) or the hardener component b) is selectively applied alone or together with other components, the viscosity should be adjusted accordingly according to the application method. For application by a print head, the viscosity (Brookfield, 25 ℃, spindle 21, DIN EN ISO 2555) should be from about 2 to about 70mPas, preferably from about 5 to about 60mPas, more preferably from about 5 to about 50mPas.

When the adhesive component a) or the hardener component b) is selectively applied alone or together with other components, the surface tension should be adjusted accordingly according to the application method. For application by the print head, the surface tension should be from about 10 to about 70mN/m, preferably from about 15 to about 60mN/m, more preferably from about 15 to about 55mN/m, and especially preferably from about 20 to about 50mN/m, measured at 20 ℃ using the Wilhelmy plate method and the Kruss K100 force tensiometer.

Step (v): (iv) optionally repeating steps (ii), (iii) and (iv) one or more times

In step (v), steps (ii), (iii) and (iv) may be repeated once or several times. Preferably, the steps are repeated one or more times.

By repeating steps (ii), (iii) and (iv), it is possible to build up even shaped bodies of complex shape step by step. The number of repetitions is predetermined by the size of the molded body and the thickness of each layer, and may be more than 1000 in some cases.

The number of repetition is not particularly limited, and may be, for example, about 2 to about 10000 times, preferably about 2 to about 5000 times, more preferably about 5 to about 2500 times, and even more preferably about 10 to about 1000 times.

Optionally, there may be additional process steps after the method. For example, curing may be performed after layer-by-layer fabrication is complete. This is not particularly limited; all known curing methods can be used. Preferably, curing is carried out in an oven or by microwaves.

If necessary, the uncured coherent mass of starting material can be removed from the at least partially cured shaped body.

Of course, any and all combinations of the preferred embodiments described herein are encompassed by the present invention.

According to a first preferred alternative, the method of the invention comprises at least the following steps:

ia) preparing a mixture of the flame-resistant molding material and the hardener component b).

For this step, the flame-resistant molding materials are preferably used in an amount of at least about 80% by weight, more preferably at least about 90% by weight, and particularly preferably at least about 95% by weight, based on the molding material.

The amount of hardener component b) is preferably from about 0.05 to about 1.5% by weight, more preferably from about 0.01 to 1.25% by weight, particularly preferably from about 0.05 to about 1% by weight, based on the amount of molding material mixture taken as 100% by weight.

ib) provides a layer of a mixture of flame-resistant molding material and hardener component b).

ic) selectively applying component a) to at least a portion of said layer.

Component a) is applied to the areas to be cured of the spread mixture of fire-resistant molding material and hardener component b).

The amount of component a) may be from about 0.1 to about 5% by weight, preferably from about 0.3 to about 4% by weight, more preferably from about 0.5 to 3% by weight, based on the molding material mixture.

id) if desired, steps ib) and ic) can be repeated once or several times.

According to a second preferred alternative, the method of the invention comprises at least the following steps:

iia) preparing a mixture of the flame-resistant molding material and component a).

For this step, the flame-resistant molding materials are preferably used in an amount of at least about 80% by weight, more preferably at least about 90% by weight, and particularly preferably at least about 95% by weight, based on the molding material mixture. In one embodiment, the amount of the flame-resistant molding material may be 100% by weight, based on the molding material mixture.

Component a) may be used in amounts of from about 0.1 to about 5.3% by weight, preferably from 0.3 to about 4.3% by weight, more preferably from about 0.5 to 3.1% by weight, of component a), based on the flame-resistant molding material, and from about 0.1 to about 5% by weight, preferably from about 0.3 to about 4% by weight, more preferably from about 0.5 to about 3% by weight, based on the molding material mixture.

iib) provides a layer of a mixture of the flame-resistant molding material and component a).

iic) optionally applying a hardener component b) onto at least a part of the layer.

The hardener component b) is applied to the areas to be cured of the spread mixture of the flame-resistant molding material and component a).

The amount of hardener component b) is preferably from about 0.05 to about 1.5% by weight, more preferably from about 0.05 to 1.25% by weight, particularly preferably from about 0.05 to about 1% by weight, based on the amount of molding material mixture taken as 100% by weight.

iid) steps iib) and iic) may be repeated one or several times, if desired.

According to a third preferred alternative, the method of the invention comprises at least the following steps:

iii) A layer of fire resistant molding material is provided.

iiib 1) the hardener component b) is applied onto the surface of the layer (e.g. the entire surface of the refractory molding material) by a first applicator (e.g. by a first print head).

iiib 2) component a) is selectively applied by a second applicator (e.g. by a second print head) onto at least a part of the layer applied with hardener component b).

iid) the steps iiia), iiib 1) and iiib 2) can be repeated once or several times, if desired.

According to a fourth preferred alternative, the method of the invention comprises at least the following steps:

iva) providing a layer of fire resistant moulding material.

ivb 1) component a) is applied onto a surface of the layer (e.g. the entire surface of the refractory molding material) by a first applicator (e.g. by a first print head).

ivb 2) selectively applying a hardener component b) by a second applicator (e.g. by a second print head) onto at least a part of the layer to which component a) is applied.

ivc) the steps iva), ivb 1) and ivb 2) can be repeated once or several times, if desired.

The explanations regarding the process steps and the amounts of the components in connection with the first and second alternative apply analogously also to the third and fourth alternative.

It goes without saying that the explanations given with respect to the steps of the method according to the invention apply to the first, second, third and fourth alternative, respectively.

All optional components discussed within the framework of the present invention can of course optionally be used in alternatives 1 to 4.

The term "molding material mixture" refers to the total composition comprising all components immediately before curing, but is limited to the fact that at least component a), hardener component b) and molding material are present in the respective volume parts, thereby enabling the volume parts to cure. The volume in the work box which does not contain hardener component b) or component a) does not belong to the molding material mixture, but is identified as a mixture consisting of a fire-resistant molding material and component a), or a mixture consisting of a fire-resistant molding material and hardener component b).

Examples

The present invention will be explained in more detail by examples, but is not limited thereto.

All proportions and percentages are by weight unless otherwise indicated.

Example 1: investigation of adhesion reduction

0.3% by weight of hardener was added to the sand GS 19 (average particle size 0.19 mm) ((Molding material mixture 1) Or sand GS 19 with another 0.2 wt% of a powdered additive (amorphous SiO) ₂ Trade name INOTEC promoter EP 4500 available from ASK Chemicals GmbH company: (Molding material mixture 2) Two molding material mixtures of composition, and the mixtures were homogenized in a paddle mixer to evaluate the tendency of unbonded sand to adhere to the bonded parts in the layer-by-layer production of three-dimensional bodies.

Curing agent 1Is a mixture of 65% p-toluenesulfonic acid and 35% water.

Hardening agent 2Is a mixture of 35% p-toluenesulfonic acid, 35% xylenesulfonic acid and 30% water.

Hardening agent 3Is a mixture of 50% methanesulfonic acid, 45% water and 5% monoethylene glycol (MEG).

Curing agent 4Is a mixture of 65% p-toluene sulfonic acid, 35% water and 5% monoethylene glycol (MEG).

Test pieces were prepared on a commercially available printing system (VX 200 available from Voxeljet AG). As component a) a commercially available furan resin (Askuran 3D 120, from ASK Chemicals GmbH) containing 87% by weight of furfuryl alcohol was used. In all tests, the amount of component a) was set to 2 parts by weight, based on 100 parts by weight of the molding material mixture.

Test pieces were printed to determine the flexural strength (dimensions 18.4 mm. Times.18.4 mm. Times.100 mm) and tested on a universal tester (Zwick Z010).

A specific specimen geometry was created to quantify the sticking that occurred during the preparation process. The geometry and corresponding dimensions are shown in fig. 1. The dimensions of the holes shown in FIG. 1 are listed in Table 1.

Table 1: hole size in FIG. 1

Numbering of holes	Diameter of hole [ mm ]]
		1	13
2	12
		3	11
4	10
		5	9
6	8
		7	7
8	5
		9	4
10	3

After the test piece was prepared, the adhered sand was completely removed from the top and bottom sides and outer edges of the test piece with a spatula, leaving only the sand in the holes of the test piece geometry. This is done with as little vibration as possible so as not to simultaneously remove the sand in the holes. Then, the test piece was placed on a sieve and placed on a vibrating plate (Multiserv LUZ-2 e). The vibrating plate was induced with an amplitude of 0.01 for a time period of 5 seconds and the process was repeated 12 times. Therefore, the total vibration time was 60 seconds. Subsequently, it was visually evaluated how many and which pores were opened due to the vibration, thereby removing the sand grain adhesion. Since both the preparation of the test pieces and the induced vibrations remain constant, the test allows an assessment of the sand adhesion caused by the material system used therein. The test results are shown in table 2.

Table 2: strength and Sand adhesion evaluation of the different Molding Material mixtures and hardeners during printing on a VX 200 Press 2%

This test shows that the use of the hardener component used according to the invention leads to a significant reduction in the sand adhesion in the resulting test pieces (see table 2). Meanwhile, the strength of the test piece is not affected. The hardener component used in the process of the invention therefore allows a significant reduction in the adhesion occurring during preparation and in the required post-treatments, without negatively affecting the strength of the remaining test pieces obtained.

Example 2:

test pieces with different acids as hardener components were prepared based on the method discussed in example 1 using the molding material mixture 2 from example 1 and the treatment of example 1.

Test piece 4 of the present invention shows excellent strength and very low sand adhesion.

Test 5 of the present invention having benzenesulfonic acid and methanesulfonic acid showed slightly higher strength than test 4, but also showed slightly higher sand adhesion. However, it also showed good results.

Comparative samples C-1 and C-2 showed significant sand adhesion, which required extensive post-treatment of the samples.

Comparative test piece C-3 exhibited low strength, which limited its practical application.

Claims

1. A method for producing a cured three-dimensional shaped body layer by layer, wherein the method at least comprises:

(i) Providing an adhesive comprising at least the following components:

(v) (iv) optionally repeating steps (ii), (iii) and (iv) once or several times.

2. The method according to claim 1, wherein the method comprises at least:

a) Preparing a mixture of a flame-resistant molding material and a hardener component b),

b) Providing a layer of a mixture of a flame-resistant moulding material and a hardener component b),

c) Optionally applying a) component of monomeric furfuryl alcohol and optionally a resin component to at least a portion of the layer, and

d) Optionally repeating steps B) and C) once or several times.

3. The method according to claim 1, wherein the method comprises at least:

a) Preparing a flame-resistant molding material and a mixture of monomeric furfuryl alcohol and optionally a component a) of a resin component,

b) Providing a layer of a mixture of a flame-resistant molding material and component a),

c) Optionally applying a hardener component b) to at least a part of the layer, and

d) Optionally repeating steps B) and C) once or several times.

4. The method according to claim 1, wherein the method comprises at least:

a) A layer of a fire-resistant moulding material is provided,

b) Applying component a) of monomeric furfuryl alcohol and optionally a resin component to the surface of the layer,

c) Selectively applying a hardener component b) to at least a part of the layer to which component a) is applied, and

d) Optionally repeating steps A), B) and C) once or several times.

5. The method according to claim 1, wherein the method comprises at least:

a) Providing a layer of a fire-resistant molding material,

b) Applying a hardener component b) onto the surface of the layer,

c) Optionally applying a) component of monomeric furfuryl alcohol and optionally a resin component to at least a part of the layer to which the hardener component b) is applied, and

d) Optionally repeating steps A), B) and C) once or several times.

6. A process according to any one of claims 1-5 wherein said binder comprises from about 60 to about 98 weight percent monomeric furfuryl alcohol, based on the sum of the resin component and the monomeric furfuryl alcohol.

7. The method of any of claims 1-6, wherein the selective applying is performed by a printhead.

8. The method of claim 7, wherein the selective application is by jet printing.

9. A shaped body obtainable by the process according to any one of claims 1 to 8.

10. Use of the shaped bodies according to claim 9 in metal casting, in particular iron, steel, copper or aluminum casting.